Response of mustard to varying levels of irrigation and nitrogen

Introduction

Mustard (Brassica juncea) is one of the most significant oilseeds crops globally, with its cultivation expanding due to rising demand for edible oils. In 2023, India emerged as the world's leading producer of mustard seed, contributing approximately 12 million tonnes.

During the 2023-24 rabi season, the country achieved a record production of 120.9 lakh tonnes, cultivated over an estimated 100.6 lakh hectares, resulting in an average yield of 1,201 kg/ha. Among the leading mustard-producing states, Madhya Pradesh made a substantial contribution. The state recorded a production of nearly 17.6 lakh tonnes, with about 13.98 lakh hectares under mustard cultivation, yielding an average of 1,258 kg/ha. Given its consistent output, Madhya Pradesh holds a strategic position in India's oilseed economy, making it a priority region for agronomic advancements. Mustard (Brassica spp.) is cultivated widely across a range of agro-climatic zones, particularly thriving in dry and semidry regions where water shortages and soil fertility constraints often hinder crop productivity. As the global emphasis on sustainable agriculture and edible oil production intensifies, improving the efficiency of resource utilization in mustard farming becomes increasingly important. Among the key agronomic factors, irrigation and nitrogen management play crucial roles in influencing the crop's growth, yield potential, and quality. Inadequate water availability during critical growth stages can severely restrict plant development and seed formation. Likewise, inefficient nitrogen use can result in poor nutrient absorption, decreased yields, and adverse environmental effects. Mulching, on the other hand, has gained prominence for its role in conserving soil moisture, moderating soil temperature, reducing weed growth, and improving nutrient retention. Its integration into crop management could significantly influence how mustard responds to both irrigation and nutrient application. However, while each of these practices-irrigation, nitrogen management, and mulching-has demonstrated individual benefits, there is limited research on their combined or interactive effects on mustard performance, especially under the resource-constrained conditions prevalent in regions like Madhya Pradesh.

This research is therefore designed to investigate the response of mustard to different irrigation and nitrogen levels, with and without the application of mulch. The objective is to identify the most effective combinations that can maximize yield, enhance resource-use efficiency, and promote environmentally sustainable practices. The outcomes of this study are expected to support the development of integrated crop management strategies suitable for diverse growing conditions.

Materials and Methods

A field experiment entitled "Response of mustard to levels of irrigation and nitrogen with and without mulch" was conducted during Rabi season of 2024-25. The details of experimental techniques followed, material used and criteria adopted for treatment evaluation during the course of investigation are described in this chapter under appropriate headings. The experiment was laid out at the SAGE Agriculture field, School of Agriculture, SAGE University, Bhopal, Madhya Pradesh, The experimental site is situated geographically at 23°16' N latitude and 77°36' E longitude, with an elevation of 500 meters above sea level. The experiment was designed using a Randomized Block Design, resulting in main treatments 2 and sub treatments 4 each replicated three times. Observations to be recorded on mustard crop plant populationm2, plant height(cm.) number of branched per plant (Primary and secondary) Dry matter accumulation, Number of siliques per plant, Number of seeds silique, 100 seed weight (g.) Biological yield (kg plot - 1 ), Seed yield (kg plot -1 ) and Harvest index (%). Experimental data were analysed using analysis of variance (ANOVA) as per randomized block design (RBD). The significance of the treatments was tested using F test with 5% level of significance (p<0.05) and means were compared using the critical difference (CD) test at α = 0.05.

MS Excel 2013 was used to analyse the experimental data for its test of significance.

Result and Discussions

Growth attributes: Growth attributes of mustard, i.e. plant population, plant height, dry matter accumulation, number of branches (primary and secondary) were recorded at 30, 60, 90 days (DAS) and at harvest.

Plant population:

The plant population at 30 DAS and at harvest was not significantly affected by irrigation levels, nitrogen levels, or their interaction. However, a higher plant population (8.6 1, although these differences were not statistically significant. This suggests that the early establishment and final stand density of plants were not markedly influenced by irrigation level or mulching practices, corroborating findings by Jha, A., & Kumar, S. (2024) [2] . As nitrogen levels increased, plant height also showed a consistent rise, with the maximum height (143.66 cm) recorded at 125% RDN, significantly exceeding the plant heights at lower nitrogen levels. The interaction between irrigation and nitrogen levels was significant only at 60 and 90 DAS, but not at 30 DAS or at harvest Table 2. The increase in plant height can be attributed to the adequate moisture availability in the rhizosphere, which created a favourable growth environment. This improved cell elongation, turgidity, stomatal opening, and efficient partitioning of photosynthates to the sink. In contrast, possibly exposing the crop to more moisture stress at various stages of its water requirement.

Number of branches (Primary):

The number of primary branches was significantly affected by irrigation, mulch, and nitrogen levels. Irrigation at 0.09 IW/CPE with mulch recorded significantly higher branches (6.83) at harvest compared to 0.06 IW/CPE without mulch (5.41). An increase in nitrogen levels also resulted in a significant rise in the number of primary branches, with the maximum (7.50) recorded under 125% RDN Table 3. The interaction effect between irrigation and nitrogen levels was non-significant at 30 DAS and harvest, but significant at 60 and 90 DAS. This aligns with findings by Meena et al. (2023) [17] Narayan et al. (2020) [3] , who observed increased branching under higher irrigation and mulch treatments in legumes. Nitrogen application had a significant and positive effect at all stages. 4. The interaction between irrigation and nitrogen levels was significant at 60 and 90 DAS but non-significant at harvest. Nitrogen application showed a positive and significant influence on branch formation.

Dry matter accumulation:

The dry matter accumulation was not significantly affected by irrigation and mulch treatments at any stage of crop growth. However, nitrogen levels showed a significant effect at all stages. The highest dry matter accumulation (27.71 g/plant at harvest) was recorded under 125% RDN, which was significantly superior to lower nitrogen levels Table 5. The interaction between irrigation and nitrogen levels was found to be nonsignificant at all stages Patel et al. (2013) [5] .

Number of silique per plant:

The number of silique per plant at harvest was significantly influenced by both irrigation and nitrogen levels. Irrigation at 0.09 IW/CPE with mulch recorded a significantly higher number of silique (79.90) compared to 0.06 IW/CPE without mulch (78.89). Among nitrogen treatments, the highest number of silique (80.92) was observed at 125% RDN, which was significantly superior to lower nitrogen levels Table 6. The interaction effect between irrigation and nitrogen was also found to be significant, Patel et al. (2015) [6] . Among nitrogen treatments, the maximum number of seeds per silique (20.87) was obtained with 125% RDN, which was significantly higher than the lower nitrogen levels Table 7. The interaction between irrigation and nitrogen was also found to be significant. Although the difference was not statistically significant, the trend suggests that improved soil moisture and temperature regulation under mulch may enhance flowering and pod setting, consistent with the findings of Patel et al. (2017) [8] , who reported improved reproductive traits under mulched conditions. RDN produced the maximum test weight (5.32 g), significantly superior to all other nitrogen levels. The interaction effect between irrigation and nitrogen was also found to be significant Table 8. The increase may be attributed to improved soil moisture and nutrient availability under mulched conditions, which enhances fertilization and seed setting, as supported by Meena et al. (2023) [17] , who reported similar improvements in seed yield attributes under mulching in oilseed crops. 8. The interaction effect between irrigation and nitrogen was also significant for all parameters Raj et al. (2021) [13] . Biological yield: The data on biological yield at harvest was significantly influenced by both irrigation and nitrogen levels. Higher biological yield (5338.00 kg/ha) was recorded under 0.09 IW/CPE with mulch compared to 0.06 IW/CPE without mulch (5123.25 kg/ha). Among nitrogen treatments, the maximum biological yield (5665.50 kg/ha) was observed with 125% RDN, which was significantly superior to other nitrogen levels. The interaction between irrigation and nitrogen was also significant. The improvement in biological yield under mulched conditions may be due to better soil moisture conservation, enhanced root growth, and improved overall plant vigour. These results are consistent with the findings of Raj et al. (2019) [12] , who reported increased biomass production in oilseed crops under mulched and optimally irrigated conditions.

Oil content in seeds:

The data on protein and oil content in seeds were significantly influenced by both irrigation and nitrogen levels. Irrigation at 0.09 IW/CPE with mulch resulted in significantly higher protein content (22.88%) and oil content (40.13%) compared to 0.06 IW/CPE without mulch. Among nitrogen levels, the highest protein (23.87%) and oil content (40.92%) were recorded under 125% RDN, which was significantly superior to the lower nitrogen levels Table 10. The interaction between irrigation and nitrogen was also found to be significant for both parameters. These findings are in agreement with Meena et al. (2023) [17] , who reported enhanced seed composition in oilseed crops under mulched irrigation.

Soil properties Soil chemical pH, and electrical conductivity:

The soil pH and electrical conductivity after sowing were significantly affected by both irrigation and nitrogen levels. Higher pH (7.39) and electrical conductivity (0.22 dS/m) were observed under 0.09 IW/CPE with mulch compared to 0.06 IW/CPE without mulch. Among nitrogen treatments, the highest pH (7.46) and electrical conductivity (0.24 dS/m) were recorded under 125% RDN, which were significantly superior to other levels. However, the interaction effect between irrigation and nitrogen levels was found to be non-significant for both parameters Table 11. This slight increase in soil pH and EC could be due to enhanced mineralization and solute movement under better moisture conditions, as also observed by Rajput et al. (2016) [14] , who reported improved nutrient solubility under mulched irrigation in oilseed crops. Organic carbon: The data on organic carbon content in soil was significantly influenced by both irrigation and nitrogen levels. Irrigation at 0.09 IW/CPE with mulch recorded significantly higher organic carbon (0.75%) compared to 0.06 IW/CPE without mulch (0.59%) Table 12. Among nitrogen levels, the highest organic carbon (0.79%) was observed with 125% RDN, which was significantly superior to the other treatments. The interaction between irrigation and nitrogen was found to be non-significant. The increased organic carbon under mulched irrigation is likely due to improved moisture retention, microbial activity, and reduced organic matter decomposition losses, aligning with the findings of Patel et al. (2020) [20] , Yadav et al. (2021) [13] , who noted mulch-induced enhancement in SOC due to moderated soil temperature and reduced erosion. [11] .

Conclusion

The study found that irrigating mustard at critical growth stages, especially during branching and flowering, significantly improved both growth and yield. Two irrigations proved more effective than one or no irrigation in enhancing water use efficiency and seed yield. Maintaining adequate moisture during the reproductive phase, particularly during flowering, was essential to prevent flower drop and ensure proper seed setting. Applying up to 120 kg/ha of nitrogen boosted plant growth and yield, with the best results achieved when combined with optimal irrigation and mulch. Mulch played a key role in conserving moisture, reducing evaporation, and promoting microbial activity, all of which contributed to higher yields and healthier soil. The combination of two irrigations, 120 kg N/ha, and mulch was the most effective for improving growth, yield, and economic returns. This treatment also optimized water use efficiency, while excess irrigation decreased efficiency and caused nutrient leaching.

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